Pulse rate monitor



Patented May 29, 1951 1 `PULSE RATE l. MONITGR 'Robert Y"Beagles;'Collingswood,N. "J.; assigner to ilRadid-/Corporaton of America, acolporationf Application September 29,1944,Serial-No. 556,338

,This invention. relates. to' a. pulse. ratemonitor ...and has particular reference to a' device fordeter- I.mining whether pulses recur at a "desired'repeti- .tion rate, or `at one-half or some other fraction off. said rate.

A type ofplserate monitor in frequent use consists of. an oscilloscope, to the verticad'e'iiection platesof which thep'ulses to be monitored .are.applied, while asweep voltage wave of afrev :.quency equal. to "the desired. pulse repetitionv rate .is applied tofthehorizontaldeflection plates. YIf v .xthe'. actual repetitionrate of.` the monitoredpulses .isequal tothe sweep1rate,a'fsin"gle pulse or"pip yappears on thescreenof lthe. oscilloscope.

It sometimeslhappens, however, particularly with Vself-pulsed power .oscillators of the A.type V.used in. radar equipment, that-.a misadjustm'ent .0f...the..oscillator. occurs,. as a, result of which the .real pulse repetition rate is .one-half .of the 'desiredrate. Theordinary type of monitor, 'Las just outlined, does not.` detect this misadjustment, ,because the indication which it ,gives in such ,cases .is .thesameas though .the repetition rate l,were correct, namely, a single pip.

(At very low f frequenciesif 'the desired repeti- .tionrate is, say, fipulsesper second, amisadjustment which producesa pulse rate of 30`pulses v,per Asecond may result in .a barely .discernible Y iiickerf' the Vsingle,v pulse for pip which appears onthe screen of the oscilloscope;butthisis a very runreliable'indication,"Tandat higherfre- `quencies' the flicker cannot be seenat all.

It is, therefore, an' object of the'invention to provide means .for indicating .a change `inthe ...rate ofpulsing Aof a pulsegenerator.

`It`is aparticlar object of `tl'ieinvention to ,provide an improved method of and meansffor ,determining when-a self-pulsed oscillator `,gen- ,.erates.pulses .athalir a 'desiredrate or at some .otherffraction of said rate.

Another .object of fthe invention is to. provide Van improvedpulse, rate monitor.

..An..additional object oflthe inventionisto provide simple, compact and .improved `equipment by., means .ofwhich A.an easily identifiablev indication-of .half-rate pulsing of a self-pulsed oscillatonmaybe obtained.

These objects .are achieved according to the invention by deiiecting an Velectron beam4 in one `.plane bymeans of :the pulses to be monitored, .anddefiecting the same beam in another plane 'by means of a sweep voltage Ywave Whosefrequencyis one-half of the desiredpulse repetition rate. .An indication .of 'the deflected beam is then f. btained, for.. example;V by projecting lthefbeam onthe screen ofanioscilloscope. If the'monitored i pulses 'recur at'the desiredrate, two pulses or f pip's`will be'seenf on the screen; but if the pulse 'fgenerator'has"not.'.been properly yadjusted and half-rate .pulsing occurs, only one pip will .'app'ear.

In an embodiment of the invention hereinafter morel fully described and applicable to self -pulsed poweroscillators, the' sweep voltage wave having a frequency of 'half' the desired pulse repetition "rate isderived from a sine waveiaudio frequency oscillatorwhich provides a triggering voltage'for "thepower voscillator 5 and .determines the pulse =repetition rate; a 2:1 (frequency stepdown) l5 "multivibrator converts the sine wave audio Vfre- Avquency output ofthis oscillator .into a saw-tooth Wave' sweep voltage of the desired frequency.

The .following description .of the invention ,shouldzbe read in conjunction with the accom- 'panying. drawing, in which:

Figure 1 isa'block diagram of;relevant'por tions of a self-'pulsed power'oscillator including 'Jtheipulse rate monitor of the present invention, Figure 2..is a schematic diagram of the multivibrator and.sweepgeneratorshown in block yin "Figure l.1,

V Figuresl3 ,and 4are views of indications Aap- ,..pearing on .lthescreenof thecathode ray tube .-.oflFigure lwithdifferent connections from those 3o. of .Eigure.,1,; and

Figure` 5;.is-a diagram showing` a portion ofthe ..circuitconnections .to obtain the indication of .-iEigure A.

vRef1erring-. to Fig. 1,1al transmitter-oscillator 52 .35.igenerates `oscillations lata .frequency of, 4say,

'200 megacy'cles per second. A sine-waveoscil- .1.lator.22.. havingV a .frequency -of- 200 cycles per second...forexampla isv connected to the trans- .,-mitter-oscillator .through a-trigger-generator cir- A lo ...cuit indicatedat BIL-which converts. the sine-wave .output .ofthe oscillator .'22 into sharply defined pulses recurring atthe Ysame, frequency, viz. 200 .c. p. s., and whichkeyor trigger. the transmitter- ..os'c`il1ator`62. .The output of "the latter device consists, ythereforarofA pulses of radio frequency energyat a'frequency equal to, and determined "by" the' frequency of the oscillator 22.

A'lradiofrequency 'tuned'resonator l''is coupled in any appropriate "manner to the transmitter- `60 'oscillator 62, and receives the pulses which that "devicetransmitsL '.Theoutput of the resonator isapplie'd toaradiofrequency rectier l2 which removes the radio frequency component; leaving 'La rectangiilanpulseiasindicated` in'Fig. 1. A "portion `cf 'the rectified output is vthenapplied present invention is more intimately concerned,

is applied through conductive path 2u and an isolating diode and pulse broadener 24 to Avertical deecting plates 26a, 2Gb of a cathode ray tube 28. If necessary, a pulse amplifier 3l] may be included in the conductive path 20.

The sine wave voltage output, of the audio frequency oscillator 22 is fed to a multivibrator or sweep circuit 32, which may be that described in U. S. Patent No. 2,157,434 to J. L. Potter, and a preferred form of which is shown in Fig. 2.

In this form, the multivibrator 32`includes a twin triode 34, which may be an RCA Type 6N7, and has an input terminal 36 connected to the control grid 38 of one of the triodes through al variable resistor 4G. As in conventional multivibrators, the anodes 42 and M, respectively, of the two triodes are connected through an anode resistor 45, and their cathodes 48 and 50, respectively, are connected by a conductor 52. anode circuit of the triode shown on the righthand side of Fig. 2 also includes a resistor 54, a capacitor 56 and an output terminal 58. The resistor 54 and capacitor 56 form a time constant network which converts the normally rectangular i wave output of the multivibrator into a sawtooth wave voltage, and the circuit parameters are so chosen as to create a frequency stepdown of 2:1, so that the frequency of the output sawtooth wave is 100 cycles per second. This output wave is applied to horizontal deflecting plates Ella, 55h of the cathode ray tube 28.

If the power oscillator is properly adjusted so that the repetition rate of the pulses applied to the vertical deflecting plates 26a, 26h is equal to the frequency of the audio frequency oscillator 22, two pulses or pips will appear on the screen of the cathode ray tube, because the electron beam in that tube will be deected vertically by the monitored pulses twice for each horizontal sweep. If, however, the power oscillator has not been properly adjusted and half-rate pulsing results, only one pip will be seen on the screen lof the cathode ray tube. The maladjustment will thus be immediately detected, and appropriate steps may then be taken to secure proper adjustment.

While the invention has been described primarily with reference to the detection of halfrate pulsing, it will be apparent that it is equally Y applicable to a situation where the actual repetition rate is some other undesired fraction (having the form l/n, where n is any integer 3, 4, 5 n) of the desired rate. It will then be necessary for the frequency of the sweep voltage to be the same fraction of the desired repetition rate as is the suspected undesired repetition rate.

It will further be apparent that the linvention includes any variation of an electron beam by the monitored pulses, further variation of the beam by a voltage whose frequency is a fraction of the desired pulse repetition rate, and indication of the resultant beam; and variation is to be understood here to include any variation of density or position of the beam, as well as modulation thereof.

The

The arrangement illustrated by Fig. 1 may, for example, be varied by applying the monitored pulses to the grid of the cathode ray tube instead of to the vertical deflecting plates. The sweep voltage will give a trace which is a horizontal line, and if the frequency of the sweep voltage is made half of the desired rate, this will be cut off twice by the pulses.

If, therefore, the pulse repetition rate is correct, the indication will, in this case, be a horizontal line with two holes in it (as in Fig. 3) and any other trace will be an indication of wrong pulsing.

` As an alternative to the last described arrangement, the cathode ray tube may be biased to cut-off, and the pulses employed to overcome this bias, so that the indication for correct pulsing will be two stationary dots, as illustrated by Fig. 4. Any other trace will indicate wrong pulsing. Fig. 5 is a diagram of the connections to be made to achieve this result. One branch of the conductive path 20 of Fig. 1 carrying the pulses to be monitored is connected to the grid of the cathode ray tube, indicated at 66. The other branch is connected to the cathode B2 of the tube, and hence to ground, through a source 64 of direct current which biases the tube to cut-olf, except when overcome by the monitored pulses.

There has thus been described a simple and effective method of and means for monitoring pulses, in which an electron beam is deflected in one plane by means of a saw-tooth wave sweep voltage having a frequency equal to a fraction of the desired pulse repetition rate, while the same beam is deflected in another plane by the monitored pulses, and an indication of the resultantly deflected beam is obtained. In the application of the invention to the monitoring of a self-pulsed power oscillator, the sweep voltage may be derived from the oscillator from which the triggering voltage for the power oscillator is obtained.

I claim as my invention:

l. In vapparatus for determining whether pulses of energy from a power oscillator recur at a desired rate, means for triggering said oscillator at .said desired rate including an audio frequency oscillator, means for deriving from said audio frequency oscillator a saw-tooth wave sweep voltage having a frequency equal to l/n that of said desired rate where n is a small integer, means for establishing an electron beam, means for deilecting said beam in one plane by said pulses, means for deiiecting said beam in another plane by said sweep voltage, and means for indicating the resultantly deflected beam.

2. Apparatus, according to claim l, where n is equal to 2. Y

3. In apparatus for determining whether pulses ofenergy from a power oscillator recur at a desired rate, means for triggering said oscillator at said desired rate including an audio frequency oscillator, means for deriving from said audio frequency oscillator a saw-tooth Wave sweep voltage having a frequency l/n that of said desired rate where n is a small integer, a cathode ray tube, means for establishing an electron beam in said tube, means for defiecting said beam in a plane by said sweep voltage, and means for applying said pulses to the grid of said tube.

fl. Apparatus, according to claim 3, in which said cathode ray tube is biased to cut-off and means for applying said pulses to said tube so as to overcome said bias.

5. In apparatus for determining whether pulses of energy from a, power oscillator recur as a desired rate, means for triggering said oscillator at REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date Jakel et al Oct. 31, 1939 Hansen Feb. 24, 1942 Browne et al June 16, 1942 Burnett Aug. 4, 1942 Vance Apr. 18, 1944 Brauer et a1 Nov. 26, 1946 

